Japanese Laid-Open Patent No. 2004-319334 proposes a charging and discharging inspection system of the type for a thin secondary battery, which includes clips having respective pairs of clamp members to clamp positive and negative electrode terminal parts of the battery, energization and inspection contact elements attached to tip end portions of the clamp members for power energization and voltage measurement of the battery and rotation shafts disposed between middle portions of the respective pairs of the clamp members, such that the clamp members can be opened and closed about the rotation shafts to clamp the positive and negative electrode terminal parts between their tip end portions.
In the case of a laminate type lithium ion secondary battery, a battery element including positive and negative electrodes, electrolytic solution etc. is accommodated in a laminate film package with positive and negative electrode lead terminals protruding from the laminate film package. The laminate film package is properly sealed or closed by adhering thermally fusible resin films to the positive and negative electrode lead terminals, covering the battery element with two upper and lower laminate films of the laminate film package in such a manner as to sandwich the thermally fusible resin film adhering portions of the positive and negative electrode lead terminals between peripheral edge portions of the upper and lower laminate films, and then, thermally fusing peripheries of the upper and lower laminate films. The lead terminals are made of a metal material e.g. aluminum, copper etc. and are subjected in advance to surface treatment, thereby forming insulating films to not only impart insulating properties but also improve the interfacial adhesion of the thermally fusible resin films to the lead terminals. The laminate type lithium ion secondary battery of such structure is usable as, for example, a battery cell for a lithium ion battery pack in an electric vehicle.
When the above laminate type lithium ion secondary battery is applied to the charging and discharging inspection system of Japanese Laid-Open Patent No. 2004-319334, however, the insulating films on the lead terminals cause a large electrical resistance upon connection of the clips to the lead terminals so that the system cannot smoothly perform charging and discharging inspection on the battery.
More specifically, the system checks whether the contact elements of the clips are in adequately contact with the lead terminals of the respective electrodes and measures the voltage of the battery cell before shifting to a charging and discharging inspection mode. If the contact resistance becomes excessive under the influence of the insulating films on the lead terminals as mentioned above, the system cannot correctly measure the voltage of the battery cell and cannot shift to charging and discharging operation. The system of Japanese Laid-Open Patent No. 2004-319334 is thus not adaptable to the battery where the insulating films are formed on the lead terminals. There is still room for improvement in the charging and discharging inspection system.